Start two weeks beforehand.
Decide how many guests you'll have at least two weeks beforehand, and assess how much space you have, both at the table and in your home. Compose your menu at least two weeks ahead of time as well. Plan for each person to eat between one and two pounds of food.
Ready the refrigerator.
Clean out as much of the refrigerator as possible one week ahead. Be ruthless in your decisions about what to toss. The more free space in the fridge, the better.
Do the big grocery shop a week before.
Make the big trip to the grocery store a week ahead. Most items, with the exception of salad greens and some fruit, will keep for a week.
Get dessert out of the way.
If you're baking cookies for the party, prepare the cookie dough in advance and freeze it. If you're serving a decorated cake, make and bake the cake parts a week or more ahead of time, wrap them well in plastic wrap and freeze them until the day before. Frozen cakes are easier to decorate than thawed ones anyway.
Set the table – and consider serving buffet style.
If doing a sit-down dinner, set the table two days ahead. This will give you enough time to buy or borrow extra dinnerware or chairs.
If you want to serve more guests than your table will seat, serve the meal buffet-style. Set your table against a wall near the kitchen and use it as the serving area. For buffet service, make sure to divide all the food into small portions.
Cook ahead as much as possible.
Make as many dishes the day before as you can. Prepare and chill desserts, make seasoning mixes and make or start accompanying sauces. And plan on serving some food that doesn't need to be cooked, like salad, cheese and crackers, and fresh fruit.
Peel and cut all vegetables two days before.
Carrots and potatoes can be stored in ice water in the fridge; onions, celery and other vegetables must be kept dry and wrapped well.
Prep the star of the dinner.
Trim and ready your roast beef or turkey for the oven, if applicable. Place it in the roasting pan and chill until needed. Don't season it ahead of time, though.
Time arrivals right.
Plan your guests' arrival to give you enough time to cook.